Previous research on this project indicates that the nature of the attachment figure has a pervasive and abiding influence on the rhesus monkey's basic stance toward the environment and its ways of coping with change. Monkeys raised with unresponsive substitute mothers are passive in their approach to novel environmental events. In such situations, locomotion, vocalization, manual and visual contacts with the environment, defecation, heart rate, and plasma cortisol and relatively low. In contrast, monkeys raised with responsive mother substitutes are active in their approach to novel environmental events. Locomotion, vocalization, manual and visual contacts with the environment, defecation, heart rate, and plasma cortisol are relatively high. Seemingly, a monkey raised with an inert surrogate, which makes no demands and occassions no surprises, extrapolates from this experience to its relations with the world in general, whereas a monkey raised with a more dynamic attachment figure, which requires that it make active efforts to accommodate to changing circumstances, approaches new situations as though they were potentially amenable to its control. Many research possibilities are raised by these findings. An immediate need, however, is to document what appears to be the major distinction between rearing groups, namely, the organization of their responses to stressful situations, particularly with regard to the development and nature of intergroup differences in stress physiology. This is the primary objective of the proposed research. Monkeys will be raised for the first three years of life with living mother substitutes or with inanimate surrogates. Effects of rearing conditions on sympathetic and parasympathetic interactions, on endocrine profiles, and on behavior will be determined by measuring activity under normal (nonstressed) conditions, and in response to a variety of experimental procedures. The onset, development generality, and persistence of intergroup differences in behavior and physiological profiles will be established by collecting longitudinal data over a broad range of situations.